There has been proposed an apparatus for successively making plastic bags each of which includes panel portions, side gusset portions and a zipper portion, as disclosed in U.S. Pat. No. 8,414,465.
In the apparatus of the patent, two webs of panel material are superposed with each other and fed longitudinally thereof. Two webs of side gusset material are supplied onto one of the webs of panel material to extend longitudinally thereof before the webs of panel material are superposed with each other. The webs of side gusset material are then sprit every a length into sheets of side gusset material, the sheets of side gusset material being spaced from each other longitudinally of the webs of panel material. In addition, a body of zipper material is supplied onto one of the webs of panel material to extend widthwise thereof, the body of zipper material being disposed between the sheets of side gusset material. The sheets of side gusset material and the body of zipper material are then interposed between the webs of panel material when the webs of panel material are superposed with each other. Furthermore, the webs of panel material and the sheets of side gusset material are heat sealed with each other longitudinally of the webs of panel material after the webs of panel material are superposed with each other. The webs of panel material and the body of zipper material are heat sealed with each other widthwise of the webs of panel material after the webs of panel material are superposed with each other. The panel portions, the side gusset portions and the zipper portion are therefore formed by the webs of panel material, the sheets of side gusset material and the body of zipper material.
In this case, the apparatus involves not only a panel material supplying device by which the webs of panel material are supplied and a zipper material supplying device by which the body of zipper material is supplied but also a side gusset material supplying device by which the webs of side gusset material are supplied. The apparatus must therefore be complicated in structure and high in cost. In addition, the apparatus is large sized by the side gusset material supplying device. A large space is therefore required for installation. When being printed with a pattern, differences in extension may come between the webs of panel material and the webs of side gusset material to be accumulated, resulting in discrepancy in pattern.
Another apparatus has also be proposed to successively make plastic bags each of which includes panel portions, side gusset portions and a bottom gusset portion, as disclosed in U.S. Pat. No. 6,692,148.
In the apparatus of the patent, a web of panel material is folded and folded back along longitudinal folded lines and longitudinal folded back line into superposed two layers having opposite side edges at each of which a folded portion is formed, the folded portion being folded into halves and interposed between the layers. The apparatus includes a Thomson blade by which one of the layers of panel material is cross cut along with the folded portions, the other layer of panel material being kept from being cross cut, so that an opening should be formed in the web of panel material. A sheet of bottom gusset material is then inserted between the layers of panel material through the opening. The side gusset portions and the bottom gusset portion can therefore be formed by the folded portions and the sheet of bottom gusset material. The webs of side gusset material have not to be supplied.
However, in the apparatus, the body of zipper material cannot be interposed between the layers of panel material by reason that the side gusset portions are formed by the folded portions. Accordingly, the apparatus can merely make the plastic bag including the bottom gusset portion. It cannot make the plastic bag including the zipper portion.
It is therefore an object of the invention to provide an apparatus which can successively make plastic bags each of which includes panel portions, side gusset portions and a zipper portion, with no web of side gusset material being supplied.